A government effort to make school meals healthier has potato growers terrified that they will lose their opportunity to cultivate young spud lovers.

“Let’s face it — the potato is not sexy,” said Chris Voigt, executive director of the Washington State Potato Commission. “It’s brown.”

The Department of Agriculture is poised to impose a one-cup-per-week limit on the amount of white potatoes served to students in school cafeterias — the latest blow to a vegetable that is already struggling with its image.

Voigt is quick to admit the American potato has a PR problem — and that traditional lobbying isn’t working. So he decided to live on nothing but potatoes for two months to prove that the vegetable is nutritious.

“We were doing all the things we were supposed to — meeting with our delegation and USDA, writing letters — and no one was listening to us,” said Voigt, who said he lost 20 pounds and lowered his cholesterol by 67 points during his potato binge that ended Nov. 30. “This is not really about lost sales or market share. Those kids are growing up thinking potatoes are bad for you.”

The new standards, which would apply to breakfasts and lunches served in public schools starting in the fall of 2012, limit starchy vegetables including white potatoes, peas, corn and lima beans to two half-cup servings a week. It would be the first update to the regulations in more than 15 years and also the first time the department has placed explicit limits on a certain food. The rules also require schools to cut back sodium and saturated fat intake and increase the amount of whole grains offered.

The department’s rules, based on research from the Institute of Medicine, are intended to encourage children to try leafy, dark vegetables such as spinach. Proponents say this is not about knocking the potato, but rather about getting children to diversify their vegetable palate.

Health advocates argue that most of the potatoes consumed in schools are greasy processed products, such as french fries and Tater Tots. While most schools have ditched deep fryers for ovens, those crispy potato sides are typically pre-fried in factories before shipping.

“This is not to vilify any one particular vegetable or class of vegetables,” USDA spokeswoman Jean Daniel said.

The potato industry, however, says the new regulations amount to a smear campaign and will ultimately hurt children, who rely on potatoes for fiber and potassium.

“If kids don’t eat it, it’s not nutrition,” said John Keeling, CEO of the National Potato Council. “They want to get children to eat more variety, and in that quest, they’ve lost sight of what’s healthy.”

Government studies have shown that the American population, children and adults alike, eat enough white potatoes and meet the requirement for fiber and potassium, the two most praised potato properties. But Americans, children in particular, do not eat enough orange and red vegetables.

Lobbyists for the potato industry knew it was only a matter of time before the potato problem hit school lunchrooms. Last year, the government said participants in a federal program for low-income pregnant women and their children couldn’t use federal money to purchase white potatoes.

Since then, groups such as the Potato Council have been pressing their case with lawmakers from potato-growing states. The Washington state potato group has already paid Beltway lobbyists $22,500 this year and dropped $90,000 in 2010 on issues including the lunch program.

Rep. Jean Schmidt (R-Ohio), chairwoman of the Agriculture Subcommittee on Nutrition and Horticulture, questioned the new potato policy in a letter last month to Agriculture Secretary Tom Vilsack signed by 40 Republicans and Democrats, including Rep. Joe Baca (Calif.), the top Democrat on Schmidt’s subcommittee.

Sen. Susan Collins (R-Maine) brandished a sack of potatoes at a hearing in March as she argued for spuds’ nutritional value over iceberg lettuce.

“Politically, it is a big deal because the potato industry has made it a big deal,” said Margo Wootan, director of nutrition policy at the Center for Science in the Public Interest. “They’ve been doing a lot of lobbying trying to get USDA to make a decision about what goes on the kids’ plates based on politics.”

The department may be sending mixed messages. Just two weeks after publishing the new school regulations in the Federal Register, the government released new dietary guidelines recommending Americans increase their intake of those same starchy vegetables. The new guidelines recommend five cups of starchy vegetables each week for a 2,000-calorie diet, up from three cups per week in the 2005 regulations.

Daniel said it could be a year and a half before the school meal regulations are brought in line with the national guidelines, as has been required by law since 1995.

Beyond potato growers, some schools are concerned that without potatoes on the menu, children will stop buying school lunches altogether, hurting already budget-strapped districts.

“If we are serving lunch with Tots, they’ll buy it,” said Doris Demers, who plans the meals at seven schools in York and Kittery, Maine. “They love their potatoes, and the thought of having them only four times a month, that will really hurt.”

Demers, whose cafeterias serve about 350,000 meals every year, buys much of the produce for her schools from local farmers to save money and incorporate fresh food into the weekly menu. She collaborated with a local potato grower to dedicate an entire field to her schools.

“We would have three or four little round funny-shaped potatoes, and the kids got a real kick out of knowing they were grown right here in their backyard,” she said.

But in the eyes of USDA regulators, a potato is a potato, whether fried, mashed or totted, imported or local, and regulators say an exception for the homegrown spud is not even on the table.